GaN基器件衬底材料β-Ga2O3单晶生长及性质研究
文献类型：学位论文
| 作者 | 张俊刚 |
| 学位类别 | 博士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐军 |
| 关键词 | GaN 衬底 β-Ga2O3 浮区法 LiGaO2/β-Ga2O3 复合衬底 |
| 其他题名 | Growth and Characterization of Single Crystal β-Ga2O3:A New Substrate Material for GaN Based Devices |
| 中文摘要 | 半导体照明产业的迅猛发展，使半导体发光器件的主要基础材料GaN基宽禁带半导体材料受到了前所未有的关注。它们物理性能优异，带隙宽、物理强度高化学性能稳定，在高亮度发光二极管、短波长半导体激光器、紫外光探测器等领域有着广泛的应用。但遗憾的是GaN单晶至今无法实现商业化，因此GaN材料的应用只能依赖于异质外延膜。目前，发展高亮度半导体照明所需要的高质量GaN薄膜受制于异质衬底，寻找新型GaN衬底材料是半导体照明产业的关键一环。 本论文顺应半导体照明产业的需要，研究了一种新型的宽禁带半导体透明导电材料——β-Ga2O3单晶的生长与性质，同时还对以β-Ga2O3单晶为基质的复合衬底材料LiGaO2/β-Ga2O3制备方法进行了详细的研究。 本论文的主要研究内容包括： 1.利用浮区法生长得到了高质量β-Ga2O3单晶。解决了单晶生长的开裂问题，能够稳定地生长超过1 cm的无宏观缺陷的单晶体。经过多次工艺改进，晶体质量有了极大的提高，其双晶摇摆曲线的半高全宽（Full width at half maximum, FWHM）仅为59.5弧秒，远远小于文献报道。 2.研究了β-Ga2O3单晶的光学性能。在β-Ga2O3单晶的吸收光谱上观察到两个位于吸收截止边上的吸收肩，并分析了该吸收肩的来源。在β-Ga2O3单晶的荧光谱上，除了紫外、蓝、绿光三种特征发光外，还首次观察到了红光发射，并探究了发光的来源。研究了退火对光谱的影响。 3.研究了β-Ga2O3单晶的电学性能，结果表明β-Ga2O3单晶的导电性能各向异性，b轴向的电导率明显高于a、c轴向，这与β-Ga2O3单晶的结构特点相关。 4.首次在β-Ga2O3单晶中观察到了上转换发光。 5.生长了不同浓度Sn4+掺杂的β-Ga2O3: Sn单晶，研究了Sn4+掺杂对β-Ga2O3单晶性能的影响，包括对光学性能、电学性能的影响。结果表明Sn4+掺杂能够抑制β-Ga2O3单晶的部分发光；电导率随着Sn4+掺杂浓度的增加而增加。 6.生长了不同浓度Cr3+掺杂的β-Ga2O3: Cr单晶，研究了它们的发光性能，探索其作为荧光衬底的可能。 7.利用气相传输平衡（VTE）技术在β-Ga2O3单晶（100）表面生成LiGaO2薄膜，构成LiGaO2/β-Ga2O3。研究结果表明VTE处理温度对LiGaO2的形成是关键因素，VTE处理温度为800℃时，VTE反应开始进行，并形成织构，当温度升高到1100℃，β-Ga2O3单晶表面形成高度<001>取向的LiGaO2薄膜。同时，VTE温度越高复合衬底的透过率越高。 8.高温退火处理使LiGaO2/β-Ga2O3复合衬底的LiGaO2薄膜随退火温度不同而呈现深浅程度不同的红色，这是因为在LiGaO2薄膜内出现色心，该色心主要与Li的挥发有关，并且，在不同退火温度下，Li空位所处格位不同，产生不同的色心。 9.利用PLD方法在β-Ga2O3衬底上制备了ZnO薄膜。研究了β-Ga2O3（100）面与ZnO(0001)面的失配率。详细研究了该ZnO薄膜的光学、电学性质。对ZnO薄膜退火处理之后发现有新相生成，ZnO薄膜的电导率下降，光学性质也发生了改变。 10.利用MOCVD方法在β-Ga2O3衬底上制备了GaN薄膜。研究计算了β-Ga2O3（100）面与GaN(0001)面的失配率。详细研究了该GaN薄膜的光致发光谱和电致发光谱。 11.将以β-Ga2O3为衬底制备的GaN薄膜制成LED，并被成功点亮，发出绿光。 |
| 英文摘要 | The wide band gap semiconductor GaN, which is the main fundamental material for semiconductor emission devices, recently has received considerable attention due to the rapid development of semiconductor lighting industry. The exceptional physical properties, notably the wide bandgap, high physical strength and outstanding chemical stability, make it ideal for many optoelectronic devices such as high light LEDs, short wave length semiconductor lasers, ultraviolet (UV) sensors. Unfortunately, GaN single crystals still aren’t commercially available. So most of its applications rely on GaN heteroepitaxial thin films deposited on foreign substrates. Recently, foreign substrates have been the bottle-neck of device quality of GaN films used for high lighting semiconductor emission. Pursuing the new GaN film substrates is now one of the most important missions for semiconductor lighting. For the development of semiconductor lighting, some new substrates for GaN films were investigate in this thesis. It is including β-Ga2O3 single crystals and β-Ga2O3 based composite substrates LiGaO2/β-Ga2O3. Not only their preparation but also their characterizations were investigated in detail. Following are the summary of the main content, 1.High quality β-Ga2O3 single crystals were successfully grown by floating zone technique. The problem of cracking was resolved and the non-macro-imperfect single crystals larger than 1 cm can be stably grown. After optimizations, the quality of the crystals were highly increased, the full width at half maximum of double crystal rocking curve was as small as 59.5 arcsec, which is much smaller than reported. 2.The optical properties of β-Ga2O3 single crystals have been studied. Two absorption shoulders in the absorption spectra have been observed and the origin has been explained. In the luminescence spectra, UV, blue and green three character emission peaks and a red one have been observed. The orgins of the emissions were investigated. 3.The electrical properties of β-Ga2O3 single crystals have been investigated. It is found that the conductivity along b axis is larger than those of a and c axis. This Anistrophy is the result of the structral particularity. 4.The upper transition in β-Ga2O3 single crystal has been observed. 5.Single crystals β-Ga2O3:Sn with different Sn4+ concentrations were successfully grown. The influences of Sn4+ concentration on optical and electrical properties were carefully studied. It is shown that Sn4+ can restrain part emission of β-Ga2O3 crystals. Conductivities increased with the increasing of Sn4+. 6.Single crystals β-Ga2O3:Cr with different Cr3+ concentrations were successfully grown. Their optical properties were investigated in detail. 7.LiGaO2/β-Ga2O3 composite substrates were fabricated by vapor transport equilibrium (VTE) technique. It is shown that the VTE temperature is the critical factor for the formation of composite substrate. At 800℃, the VTE reaction begin and the texture were formed. When increasing the temperature to 1100℃, highly <001> oriented LiGaO2 film was fabricated on β-Ga2O3 wafer. The transmission increased with the increasing of VTE temperatures. 8.After high temperature annealing the color of LiGaO2/β-Ga2O3 composite substrates changed from white to red. These phenomena are due to the color centers introduced by Li vacancies. It is found that the Li vacancies are different at different annealing temperature. 9.ZnO films were deposited on β-Ga2O3 substrates by PLD. The lattice relation between ZnO (0001) and β-Ga2O3 (100) was studied. The optical and electrical properties as well as the influence of annealing were studied in detail. It is found that anneal change their optical and electrical properties due to introducing a new phase in the films. 10.GaN films were deposited on β-Ga2O3 substrates by MOCVD. The lattice relation between GaN (0001) and β-Ga2O3 (100) was studied. The PL and EL spectra were studied in details. 11.The GaN/β-Ga2O3 based LED was successfully lightened and emit green light. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15544]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张俊刚. GaN基器件衬底材料β-Ga2O3单晶生长及性质研究[D]. 中国科学院上海光学精密机械研究所. 2007. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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